Re: SI &c., eh?

[Larry Smith <Larry.Smith@SNOW.EDU>]

At 3:12 PM -0500 8/30/1999, paul o johnson wrote:

> 3. A unit which is named after a person is written all in lower case
> (newton, volt, pascal etc.) when named in full, but starting with a
> capital letter (N V Pa etc.) when abbreviated.

Correct, as reiterated every August in the Physics Today Buyers Guide.

> An exception to this rule is the litre which, if written as a lower case
> 'l' could be mistaken for a '1' (one) and so a capital 'L' is allowed as
> an alternative. It is intended that a single letter will be decided upon
> some time in the future when it becomes clear which letter is being
> favoured most in use.

Correct again.  Physics Today says: "The symbol for liter, L, is
capitalized to avoid confusion between the letter l and the number 1."

More fun from the same article:

"Symbols for prefixes representing 10^6 or greater are capitalized.; all
others are lower case."

"There is no space between the prefix and the unit."

"Multiplication of units is indicated by inserting a raised dot or by
leaving a space between the units.  Division may be indicated by the use of
the solidus, a horizontal fraction bar or a negative exponent, but repeated
use of the solidus is not permitted."

"Unit names should not be mixed with symbols for mathematical operations.
(For example, one should write 'meter per second' but not 'meter/second' or
'meter second^-1'.  When spelling out the product of two units, a space is
recommended (although a hyphen is permissible), but one should never use a
centered dot."

"Three-digit groups in numbers with more than four digits [not 1000, Leigh]
are separated by thin spaces instead of commas to avoid confusion with the
decimal marker in European literature.  This spacing convention is also
used to the right of the decimal marker.  The numerical value and unit
symbol must be separated by a space, even when used as an adjective (for
example, 35 mm, not 33mm or 35-mm)."

"A zero should be placed in front of the decimal marker in decimal
fractions (for example, 0.3 J, not .3 J)."

Loads of fun.

Larry